Ok I really want to figure this out to get along with my stepmother?

Ok! My stepmom I don't know what she wants? I love her and she says she loves me but how do i know this?She does stuff for me but I have two stepsisters and always the youngest one ( Turning 15) always picks on me and says stuff and like i was trying to find someone on reunion for my mom and she keeps looking at my profile on there and on myspace and tells my dad i push her and hit her and tell her she is a ***** and shes fatt and no i didnt and this ONE time only one time i wrote something on my myspace because me and my friends joke about are stepparents and i was like ok no one is gonna see it but some how her daughter got it and showed it to her and they sent it to my father and now my father doesnt trust me and he told me that my stepmom told him i called her a ***** and fat and he says he doesnt know if he trusts me and like always he is on her side.I just don't know how to prove I am not lying and i want to prove to her that I do love her.